Traditionally, a cooling system of an engine installed in a construction machine mainly includes a radiator and a cooling fan. The radiator circulates cooling medium between the radiator and the engine and cools the cooling medium by outer air. The cooling fan forms air flow around the radiator and aids heat exchange of the radiator. Further, a shroud is provided between the radiator and the cooling fan to surround the radiator and the cooling fan for ensuring air flow from the radiator to the cooling fan (for example, see Patent Document 1).
In recent years, the total heat quantity of an engine is increased and therefore the water temperature of a radiator is increased. To solve such a problem, for example, the flow of air blown by a cooling fan (i.e., the flow of air passing through the vicinity of the radiator) may be increased by increasing the rotation speed of the cooling fan. However, when the rotation speed of the cooling fan is increased, noise is increased.
Accordingly, to enhance cooling capability of a cooling system of the engine, it is required to increase the flow of air blown by the cooling fan without increasing the rotation speed of the cooling fan. Various technologies for changing a shape and position of a shroud have been developed. For example, to prevent counter flow of air discharged from the cooling fan (i.e., to prevent air in the engine from returning to the radiator through the cooling fan), two cylindrical portions are provided on an end of the shroud (for example, see Patent Document 2).
Patent Document 1: JP-A-9-118141 (Published on May 6, 1997)
Patent Document 2: JP-A-2006-132380 (Published on May 25, 2006)